1. Field of the Invention
The present invention relates to a composite charged particle beam apparatus for observing a sample subjected to processing by a focused ion beam through a charged particle microscope.
2. Description of the Related Art
A focused ion beam apparatus is used for observation of a processed cross-section of a sample, production of a sample for transmission electron microscope observation, and other such purposes. Particularly in a composite charged particle beam apparatus including an electron beam apparatus, a cross-section which is under processing by a focused ion beam or a cross-section which has been processed by the focused ion beam can be observed in-situ by an electron beam. Such a composite charged particle beam apparatus is therefore widely used for successive cross-section observation and successive sample production.
In a general composite charged particle beam apparatus, the focused ion beam and the electron beam are arranged so that incident directions thereof form 90° or less, and hence the processed cross-section is observed by the electron beam from an oblique direction. In recent years, a three-dimensional analysis technology has been used in the wide field, in which images acquired for cross-section processing and its successive cross-section observation with the use of a composite charged particle beam apparatus are reconstructed into a three-dimensional image.
In the conventional composite charged particle beam apparatus, however, the processed cross-section is observed from a direction of 90° or less, and hence it is necessary to correct an observation image obtained in the oblique direction into a planar image. Further, as an observation site becomes finer, there is an increasing need for observation of a sample under processing through a scanning transmission electron microscope.
As one solution to meet the need, a technology using a composite charged particle beam apparatus in which an electron beam and a focused ion beam are orthogonally arranged is disclosed (see Japanese Patent Application Laid-open No. Hei 6-231720).
According to the apparatus thus configured, it becomes possible to observe a processed cross-section from a vertical direction without moving the sample stage. It becomes also possible to perform thickness monitoring of a thin film sample for an electron microscope and perform real-time acquisition of a scanning transmission electron microscope image by arranging a transmission electron detector in the incident direction of the electron beam.
In the case of the conventional composite charged particle beam apparatus, the ion beam and the electron beam are used to observe the same plane, for example, the same sample surface, and hence the directions of observation images acquired by the respective beams are coincident with a stage drive direction. On the other hand, in the composite charged particle beam apparatus in which two beams are orthogonally arranged, observation images acquired by the respective beams represent different orthogonal planes, for example, a sample surface and a sample side surface, and hence the vertical and horizontal directions of the respective images are not coincident with the operation directions of the axes of the stage. Therefore, the composite charged particle beam apparatus in which two beams are orthogonally arranged has a problem in that an erroneous operation is apt to occur when an operator adjusts a processing observation position of the sample while looking at the observation image of the focused ion beam or the electron beam.